This invention relates generally to couplings and more particularly to improvements in fluid-driven clutches.
A non-rotatable clutch ring is axially slidable on a shaft via a fluid introduced into a pressure chamber for transmission of the driving force through a tooth system engaged with a corresponding clutch ring having a corresponding tooth system.
A fluid-driven clutch is known from EP 0 276 255. In this are shown two controllable single clutches for a gear system which can be infinitely variably shifted under load, which clutches can be moved by a fluid into an engaged position The clutches are designed as form-locking positive denture clutches in the special form of crown gearing in which the tooth profiles of the parts to be coupled are arranged in the axial direction. Due to the axially arranged teeth, the shift distance of the parts to be coupled can be kept very short, as the specific pressure at the teeth can be kept low by the high surface area ratio of the teeth. However, the previously known sealing of the pressure chamber proved to be a drawback. The radially arranged sealing elements due to their initial tension cause unwanted additional axial friction forces when the clutch is moved. These friction forces can be determined in advance only with difficulty and are variable over the life of the clutch. Depending on the design of the flank angle of the tooth profiles, the additional axial friction force can cause the clutch to no longer uncouple automatically and to stick. A larger angle of the crown gearing can solve the problem, but the drawback arises that then the retaining force generated by the fluid must be very strong, in turn with correspondingly generously proportioned components, as a result of which the gain of space due to the crown gearing is quickly lost.